JP2002001421A - Tool for multiple hole extruder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tool for a multiple hole extruder for extruding a plurality of pipes at the same time and can reduce biased thickness of the pipe. SOLUTION: A tool which extrudes the plurality of pipes W at the same time, provided with a die case 10 wherein a plurality of charging holes 11, 12 are bores, and a plurality of dice bodies 21, 22 equipped to each charging hole 11, 12 and the dice bodies 21, 22, are porthole dies wherein a forming clearance 25 is formed by combining a female die 30 having a baring section 23 which forms an outer circumferential configuration of the pipe W and a male die having a bearing section 43 which forms an inner circumferential configuration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-hole extrusion tool for simultaneously extruding a plurality of pipes.

[0002]

2. Description of the Related Art As one means for improving the productivity of extruded materials, a porous die having a plurality of molding gaps and simultaneously extruding a plurality of extruded materials has been used. For example, a porthole double-hole die (50) for extruding a round pipe (W) shown in FIG.
The female mold (51) arranged on the front side in the pushing direction and the male mold (52) arranged on the rear side are combined. The female type (5
In 1), at the 180 ° target position of the die center line (Q ₀ ),
Two bearing portions (53) for forming the outer peripheral shape of the round pipe (W) are provided around (Q ₁ ) and (Q ₂ ), and two circular moldings are surrounded by these bearing portions (53). A hole is formed. On the other hand, the male type (52) has two of the female type (51).
In each of the corresponding positions of the two forming holes, a bearing portion (55) for forming the inner peripheral shape of the round pipe (W) is provided on the outer peripheral surface of the tip of the forming convex portion (54) projecting forward, The rear side has several port holes (5
6) penetrates the die in the front-rear direction. The bearings (55) and (55) of the male mold (52) are combined so as to fit into the two molding holes of the female mold (51), thereby forming the bearings (53) and (55) of both the molds. A molding gap (57) is formed between these two molding gaps (57).
As the extruded material passes through (57), pipes (W) and (W) having a circular cross section are simultaneously extruded.

[0003]

When a round pipe (W) is extruded using the porthole double-hole die (50), a female mold is used.
The coaxiality of the bearings (53) and (55) of the (51) and the male mold (52) is required to be good. A single-hole die with a bearing at the center of the die is manufactured by lathing, so the coaxiality between the female and male molds is high. However, in a two-hole die (50), the bearing is moved from the center of the die (Q ₀ ). It is required to be provided at the displaced positions (Q ₁ ) and (Q ₂ ). Therefore, there is a problem that the coaxiality is inferior to that of a one-hole die manufactured by lathing.

In general, in direct extrusion, a container (60)
The inner metal flow is faster at the center of the container (60) than at the wall due to frictional resistance between the billet (61) and the inner wall of the container (60). In a one-hole die, the center of the billet coincides with the center of the bearing, so even if there is a concentric difference in the metal flow, the male mold projection does not bend so that it falls down, but the two-hole die ( In the case of 50), since the centers (Q ₁ ) and (Q ₂ ) of the _two bearing portions are displaced from the center of the die (Q ₀ ), respectively, the convex part of the male mold (52) is formed.
(54) has a problem in that the extruded round pipe material (W) becomes uneven in thickness.

Further, when such an extruded raw tube having a large uneven thickness is bent, bending occurs. When the drawn tube having a low straightness is used for a photosensitive drum or a magnet roll of a laser printer, the deflection during rotation becomes large. This causes a decrease in print quality.

[0006] In view of the above technical background, an object of the present invention is to provide a porous extrusion tool that does not cause uneven thickness.

[0007]

According to the present invention, there is provided a multi-hole extrusion tool, comprising: a plurality of charging holes;
(11) A die case (10) in which (12) is drilled, and a plurality of die bodies (2) loaded in the respective loading holes (11) and (12).
1) A tool comprising (22) for simultaneously extruding a plurality of pipes (W), wherein the die bodies (21) and (22) are a bearing part (23) for forming an outer peripheral shape of the pipe (W). Are combined with a male mold (40) having a bearing portion (43) for molding the inner peripheral shape to form one molding gap (2
The basic point is that it is a porthole die in which 5) is formed.

[0008] The loading hole (11) of the die case (10)
(12), the cross-sectional shape is formed in a substantially circular shape having a linear straight part in a part of the circumferential direction, while the die main body (21) (22), the loading holes (11) (12) ) Has a substantially cylindrical shape corresponding to the inner peripheral surface, and the outer peripheral portion has the loading hole.
(11) Straight part corresponding to the straight part of (12) (31) (4
Preferably, 1) is formed.

The male die (40) of the die body (21) (22)
Has a plurality of port holes (45a) (45b) (45c) partitioned by a plurality of legs (44a) (44b) (44c), and when the die case (10) is loaded, the die case It is preferable that the cross-sectional area of the port hole (45a) located outside is larger than the cross-sectional area of the port holes (45b) (45c) located on the center side (A ₀ ) of (10). Outer port hole (45a)
Is the expansion of the port hole diameter (R ₂ ) or the port hole (45a)
It is preferable that the cross-sectional area is enlarged by enlarging the leg opening angle (α) of the leg portions (44b) and (44c) forming the angle (α) or both.

In the multi-hole extrusion tool (1) of the present invention,
Forming gap (25) formed in one die body (21) (22)
Is one, and both female (30) and male (40) bearings (3
3) Since (43) can be formed at the center of each,
High coaxiality is obtained, and the width of the molding gap (25) is formed uniformly. Furthermore, since the diameter is smaller than the conventional porous die (50) having a plurality of molding gaps, the female mold (30) and the male mold (40)
Also, the fitting accuracy with is good. The present invention employs a nesting method in which such die bodies (21) and (22) are loaded into a plurality of loading holes (11) and (12) formed in the die case (10), whereby uneven thickness is achieved. Can be extruded simultaneously. Also, when extruding pipes having different cross-sectional shapes, only the die bodies (21) and (22) need to be changed, and the die case (10) can be used in common. Can be reduced. In addition, since the surface modification treatment such as the nitriding treatment may be performed only on the small-diameter die bodies (21) and (22), the treatment cost can be reduced.

[0011] In addition, the hole (1) for loading the die case (10).
1) (12) and the die bodies (21) and (22) are provided with the corresponding straight portions (31) and (41), so that the rotation of the loaded die bodies (21) and (22) is suppressed, and the loaded state. Can be easily positioned in the circumferential direction.

Further, the male die (4) of the die body (21) (22)
In (0), the container and billet are enlarged by enlarging the cross-sectional area of the outer port hole (45a) by expanding the port hole diameter (R ₂ ), expanding the leg opening angle (α), or both. The metal flow difference caused by the frictional resistance between them can be eliminated, and the uneven thickness caused by the difference can be reduced.

[0013]

1 to 6 show an embodiment of a multi-hole extrusion tool (1) according to the present invention.

[0014] The tool (1) for multi-hole extrusion is a die case.
(10) and the same die-shaped first and second die bodies (21) and (22) to be loaded into the die case (10). The tool (1) has a plate (2) for controlling the flow of the extruded material.
6), the container (60) in which the billet (61) is loaded is arranged facing the front end opening.

As shown in FIGS. 1 and 2, the dice case (10) is 180 degrees from the center line (A ₀ ) of the dice case.
° At the target position, the first loading hole centered on (A ₁ )
(11) and a second loading hole (12) centering on (A ₂ ) are formed in the front-rear direction of the extrusion. These two loading holes (11) and (12) are connected at the intermediate portion (11a) (12a) corresponding to the outer shape of the die body (21) (22), while the two holes are integrally connected, while the front end And a hole (1
1) Circular protrusions (13), (14), (15), and (16) are formed to protrude into (12) and form a small hole opening diameter, and the two holes (11) and (12) are independent. are doing. In addition, the die case (1
(0) is the front case (17) and the rear case (1) before and after the extrusion direction.
8) and the die body in the divided state
(21) While taking in and out of (22), in the loaded state, the die body (21) by the front and rear protrusions (13) (14) (15) (16)
(22) is restrained from both front and rear directions.

As shown in FIG. 3 to FIG. 5, the first and second die bodies (21) and (22) are respectively disposed in front of the extrusion direction to form a female mold for forming an outer peripheral shape of a pipe (W). (30)
This is a porthole die in which a male die (40) arranged behind and forming an inner peripheral shape is combined. The outer shape of the die bodies (21) and (22) is substantially cylindrical, but a female type.
A circumscribed circle (39) on the outer periphery of each of (30) and male (40).
Straight portions (31) and (41) are formed by cutting out a part of (49). The first and second die bodies (21) and (22) are inserted into the first and second loading holes (11) and (12) of the die case (10), respectively, with the straight portions (31) and (41) of each other. When the first and second die bodies (21) (21) (2)
The center of ( ₂ ) coincides with the center (A ₁ ) (A ₂ ) of the first and second loading holes (11) and (12), and each of the loading holes (11) and (12).
The rotation of the die bodies (21) and (22) can be prevented.

That is, as shown in FIG. 6A, the first die main body is placed in the first loading hole (11) of the die case (10).
(21) is the straight part (31) (41) is two loading holes
(11) When loaded so as to match the connecting portion of (12), the straight portions (31) and (41) form a part of the second loading hole (12), and the second loading hole (12) A substantially linear straight portion is formed on the inner peripheral surface of the. Therefore,
The straight portions (31) and (41) of the first die body (21) correspond to the straight portions of the loading holes in the present invention. Then, as shown in FIG. 6 (B), when the second die body (12) is loaded into the second loading hole (12) in which the straight portion is formed, the second die body (22) is formed due to the presence of the straight portion.
Is prevented, and the loading position in the circumferential direction is determined. Similarly, the second die body (2) is inserted into the second loading hole (12).
By the loading of 2), a substantially straight portion is formed on the inner peripheral surface of the first loading hole (11), and the rotation of the first die body (21) is prevented. In this way, the two die bodies (2
1) and (22) prevent rotation of each other by loading them into the connected loading holes (11) and (12).

As shown in FIG. 4, the female mold (30) is provided with a bearing part (33) for forming the outer peripheral shape of the pipe (W) at a center position, and is surrounded by the bearing part (33). Thus, a circular forming hole (32) is formed. Further, a tapered relief hole (34) that opens outward toward the front is formed on the exit side of the bearing portion (33).

On the other hand, in the male mold (40), as shown in FIG. 5, the inner peripheral shape of the pipe (W) is formed on the outer peripheral surface of the leading end of the forming convex part (42) projecting forward of the center. Bearing part (4
3) and a leg (44a) on the rear side.
Three port holes (45a), (45b), and (45c), which are separated by (44b) and (44c) and through which the extruded material passes, are provided through the die in the front-rear direction. The leg portion is a straight portion (41)
Side, that is, one (44a) on the center side of the die case (10) and two on the outside (44b) (44c), for a total of three ports, and one port hole on the outside (45a) and two on the center side. (45b) and (45c) are located.

Then, as shown in FIG. 3, the female mold (30)
When these (30) and (40) are combined so that the bearing part (43) of the male mold (40) is fitted into the forming hole (32) of the bearing part (31), the two bearing parts (33) and (43) Forming gap between (25)
Is formed. Then, as shown in FIG. 1, a plurality of circular pipes (W) having a circular cross section are simultaneously extruded as the extruded material passes through the molding gap (25).

In the die bodies (21) and (22), the female mold (3
Since the bearing portions (33) and (43) of the (0) and the male die (40) are both formed at the center of the die, the coaxiality of both the bearing portions (33) and (43) is high in a combined state of these. Therefore, the molding gap (25) is formed with a uniform width all around,
A pipe (W) having a uniform thickness can be extruded. In particular, for dies that extrude round pipes, the bearings (33) (4
Since 3) can be formed by lathing, it can be made extremely coaxial.

In the die bodies (21) and (22), as shown in FIG. 4, the outer port hole (45a) of the male die (40) is larger than the center two port holes (45b) and (45c). The cross-sectional area is large. This is the center of the die case (10) (A ₀ )
This is to eliminate uneven thickness caused by a difference in distance from the object. That is, the metal flow in the container (60)
(60) Because of the frictional resistance generated between the wall surface and billet (61) surface, it is slower outside the center of the container (60),
The center of the dice case (A ₀ ) even in the dice body (21) (22)
The flow rate of the extruded material in the center side port holes (45b) and (45c) close to the center is larger than in the outer port hole (45a) far from the center (A ₀ ). This flow rate difference is the difference between the force pressing the forming protrusion (42) of the male mold (31) from the center side to the outside and the force pressing the forming protrusion (42) from the outside to the center side, causing the forming protrusion (42) to flex outward. . As a result, the width of the molding gap (25) is wider on the center side than on the outside, and the extruded pipe (W) is uneven in thickness on the center side than the outside.
In order to eliminate uneven thickness caused by such a difference in flow rate, the flow rate is increased by increasing the cross-sectional area of the outer port hole (45a), and the extruded material is increased by the inner and outer port holes (45a) (45b) (45c). It flows evenly.

As one method of enlarging the port hole cross-sectional area, the leg opening angle (α) of the two (44b) and (44c) legs forming the outer port hole (45a) is made larger than the equal angle. Opening method can be recommended. The die bodies (21) and (22) of the present embodiment have three legs, and the leg opening angle (α) is preferably 121 to 130 °, which is slightly larger than the equally divided 120 °. Note that the present invention does not limit the number of port holes to three, but preferably enlarges the range of 0.8 to 10% with respect to the equal angle.
If it is less than the lower limit, it is not sufficient to eliminate the difference between the inside and outside flow rates. If it exceeds the upper limit, the outside flow rate becomes too large, and conversely, the outside becomes thick uneven thickness.

As another method for enlarging the sectional area of the port hole, a method of enlarging the port hole diameter can be recommended. In the die bodies (21) and (22) of the present embodiment, the radius (R ₁ ) of the two port holes (45b) and (45c) on the center side and the outer port hole (45a).
Is formed such that the radius (R ₂ ) of the _first lens unit satisfies R ₁ <R ₂ . Magnification outer ports sink radius (R ₂₎ relative to the central side port sink radius (R ₁₎ is preferably in the range of 4-20%.
If it is less than the lower limit value, it is not enough to eliminate the difference between the inside and outside flow rates. If it exceeds the upper limit value, the outside flow rate becomes too large, the outside becomes thick, and the die strength decreases.

The uneven wall thickness of the pipe (W) can be reduced by either the expansion of the leg opening angle (α) or the expansion of the port hole diameter (R ₂ ). The uneven thickness can be remarkably reduced and further eliminated.

By the way, the multi-hole extrusion tool (1) of the present invention
, The outer diameter of the die body (21) (22)
The outer diameter of 0) is preferably 25 to 40%. If it is less than 25%, the diameter of the port hole cannot be sufficiently obtained, so that the welding tends to be insufficient, and there is a possibility that underfilling may occur. On the other hand, if it exceeds 40%, the strength of the die case (10) cannot be maintained. Further, it is preferable that the die bodies (21) and (22) have a sufficient port hole diameter and have a diameter as small as possible. A sufficient port hole diameter is 60 to 70% of the outer diameter of the die body in terms of diameter.
It is. Also, the loading hole (1) of the die case (10)
1) By providing a clearance between the die body (21) and the die body (21) (22), the distortion of the die case (10) during extrusion suppresses the amount of transmission to the die body (21) (22). be able to. The clearance between these is 0.05-0.2mm
Is preferably set, and particularly preferably about 0.1 mm.

[0027]

(Example 1) In the above-described tool for multi-hole extrusion (1), a maximum diameter of 80 mm was respectively inserted into the first and second loading holes (13) and (14) of a die case (10) having an outer diameter of 235 mm. , 78 mm outer diameter of straight part (31) (39) part die body (21)
(22) was loaded. The pipe (W) to be extruded is a round pipe having a diameter of 20 mm and a wall thickness of 1.4 mm, and the bearings (33) and (43) of the female die (30) and the male die (40) of the die body (10) are turned on a lathe. It is formed into a corresponding shape by processing. In addition, male type (40)
In each of the three leg portions (44a), (44b), and (44c), the opening angle of each leg is set to 120 °, and the radius (R ₁ ) of the three port holes (45a), (45b), and (45c). ) (R ₂ ) are all formed in 25mm and have three port holes (45a) (45b) (45c)
Are formed equally.

Using the extrusion die (1), JIS
A6063 aluminum alloy billet was used as an extruded material, and extruded for 24 lots.
Into a large number of test materials. 4 from these test materials
Eight pieces were extracted, and the thickness was measured to check for uneven thickness. The result is shown in FIG.

(Comparative Example 1) When extruding a round pipe of the same size as in Example 1, a two-hole porthole die (50) shown in FIG. 11 was used. In the two-hole die (50), two bearing portions (53), (53), (55), and (55) are formed at predetermined positions of the female die (51) and the male die (52) by electric discharge machining. . In the male mold (52), three port holes (56) are formed in each bearing portion (55) with the same sectional area.

Extrusion was carried out under the same conditions as in Example 1, and 96 test materials were extracted to examine uneven thickness. FIG. 8 shows the result.

(Example 2) Tool for multi-hole extrusion of Example 1
In (1), the bearing part (33) of the die body (21) (22)
Extrusion was performed under the same conditions as in Example 1 except that (43) was formed in a shape corresponding to a round pipe having a diameter of 25 mmφ and a thickness of 1.75 mm, and 148 test materials were extracted.

The thickness of these test materials was measured to check for uneven thickness. FIG. 9 shows the result.

(Comparative Example 2) In extruding a round pipe of the same size as in Example 2, a porthole double-hole die (50) equivalent to Comparative Example 1 shown in FIG. 11 was used.

Extrusion was performed under the same conditions as in Example 2, and 148 test materials were extracted to examine uneven thickness. The result is shown in FIG.

From the results shown in FIGS. 7 to 10, it was confirmed that the uneven wall thickness of the round pipe can be reduced by using a nesting type multi-hole extrusion tool loaded with a plurality of die bodies.

(Example 3) Tool for multi-hole extrusion of Example 2
In the die body (21) (22) of (1), the cross-sectional area of the outer port hole (45a) of the male die (31) was formed larger than the center side port hole (45b) (45c), and extruded. The degree of thickness deviation between the center side of the round pipe (W) (the center side of the die case) and the outside was examined. Expanding the cross-sectional area of the outer port hole (45a)
The setting is performed by setting the leg opening angle (α) of the two legs (44b) and (44c) and the outer port (45a) hole radius (R ₂ ) forming the a). Investigation was performed using round pipes made of the main bodies (17) and (18). The center port hole (45
b) The radius (R ₁ ) of (45c) was a constant value of 25 mm.

[0037]

[Table 1]

From the results shown in Table 1, in the male die (31) of the die bodies (21) and (22), the leg opening angle (α) and the port hole diameter (R ₂ ) of the legs (44b) and (44c), or It was confirmed that by expanding both of them and increasing the cross-sectional area of the outer port hole (45a), uneven wall thickness of the pipe could be further reduced.

[0039]

As described above, according to the present invention, there is provided a multi-hole extrusion tool comprising: a die case having a plurality of loading holes;
And a plurality of die bodies to be loaded into each of the loading holes, a tool for simultaneously extruding a plurality of pipes,
The die body is a porthole die in which a female mold having a bearing portion for molding the outer peripheral shape of the pipe and a male mold having a bearing portion for molding the inner peripheral shape are combined to form one molding gap. Therefore, both the female and male bearing portions can be formed at their respective centers, and a high coaxiality can be obtained so that the width of the molding gap can be made uniform. Therefore, a plurality of pipes without uneven thickness can be extruded simultaneously. Further, each die body has a smaller diameter than a conventional porous die having a plurality of molding gaps, and the good fitting accuracy between the female mold and the male mold also contributes to the reduction in uneven thickness.

Furthermore, since the die case is of a nested type in which the die body is loaded, even when extruding pipes having different cross-sectional shapes, only the die body needs to be replaced, and the die case can be used in common. Die manufacturing costs can be reduced in both costs. Also,
Since the surface modification treatment such as nitriding treatment may be performed only on the small-diameter die body, the treatment cost can be reduced.

Further, the loading hole of the die case is formed in a substantially circular shape having a cross-sectional shape having a straight straight portion in a part of the circumferential direction, while the die body is formed inside the loading hole. When a straight portion corresponding to the straight portion of the loading hole is formed in the outer peripheral portion, the rotation of the loaded die body is suppressed, and the circumferential direction in the loaded state is suppressed. Can be easily positioned.

The male die of the die main body has a plurality of port holes separated by a plurality of legs, and when the die is loaded into the die case, the port hole located on the center side of the die case is cut off. If the cross-sectional area of the port hole located outside the area is large, it is possible to eliminate the metal flow difference caused by the frictional resistance between the container and the billet and reduce uneven thickness caused by this. it can.

The cross-sectional area of the outer port hole can be easily increased by increasing the diameter of the port hole, or by increasing the angle of opening of the legs forming the port hole, or both.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a multi-hole extrusion tool according to the present invention and an extruder incorporating the multi-hole extrusion tool.

FIGS. 2A and 2B are plan views of a die case, wherein FIG. 2A is a plan view of a front case viewed from the rear, and FIG. 2B is a plan view of a rear case viewed from the rear.

FIG. 3 is a longitudinal sectional view of a die body.

FIG. 4A is a plan view of the female die of the die body as viewed from the rear, and FIG. 4B is a cross-sectional view taken along line IVB-IVB of FIG.

FIG. 5A is a plan view of the male die of the die body as viewed from the front, and FIG. 5B is a cross-sectional view taken along line VB-VB of FIG.

FIG. 6A is a cross-sectional view schematically showing a state in which only a first die body is loaded in a die case, and FIG. 6B is a schematic view showing a state in which first and second die bodies are loaded in a die case. FIG.

FIG. 7 is a graph showing a measurement result of uneven thickness of a round pipe in Example 1.

FIG. 8 is a graph showing a measurement result of uneven wall thickness of a round pipe in Comparative Example 1.

FIG. 9 is a graph showing a measurement result of uneven wall thickness of a round pipe in Example 2.

FIG. 10 is a graph showing a measurement result of uneven thickness of a round pipe in Comparative Example 2.

FIG. 11 is a longitudinal sectional view of a conventional two-hole porthole die and an extruder incorporating the two-hole porthole die.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Tool for multi-hole extrusion 10 ... Die case 11 ... Hole for 1st loading 12 ... Hole for 2nd loading 21 ... 1st die body 22 ... 2nd die body 25 ... Forming gap 30 ... Female mold 33, 43 ... Bearing Part 31, 41 ... Straight part 40 ... Male type 44a, 44b, 44c ... Leg part 45a, 45b, 45c ... Port hole α ... Leg opening angle R ₂ ... Port diameter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaki Yamanaka 6, 224 Kaiyama-cho, Sakai-shi Showa Aluminum Co., Ltd. F-term (reference) 4E029 MB03

Claims (5)

[Claims] A die case (10) having a plurality of loading holes (11) and (12) formed therein, and each of the loading holes (11) (1)
2) a tool for extruding a plurality of pipes (W) at the same time provided with a plurality of die bodies (21) and (22) to be loaded in the die (21) and (22); A female mold (30) having a bearing portion (23) for molding the outer peripheral shape and a male mold (40) having a bearing portion (43) for molding the inner peripheral shape are combined to form one molding gap ( 25. A multi-hole extrusion tool, characterized by being a porthole die formed with 25). 2. A loading hole (1) in the die case (10).
1) and (12), the cross-sectional shape is formed in a substantially circular shape having a straight straight portion in a part of the circumferential direction, while the die body (21) (22), the loading hole (11) (12) is a substantially cylindrical shape corresponding to the inner peripheral surface, and a straight portion (31) corresponding to the straight portion of the loading hole (11) (12) on the outer peripheral portion.
The tool according to claim 1, wherein (41) is formed. 3. The male die (40) of the die body (21) (22)
The die case (1) has a plurality of port holes (45a) (45b) (45c) partitioned by a plurality of legs (44a) (44b) (44c).
0), the cross-sectional area of the port hole (45a) located outside is larger than the cross-sectional area of the port holes (45b) (45c) located on the center side (A ₀ ) of the die case (10). The multi-hole extrusion tool according to claim 1 or 2, wherein the tool is formed. 4. The tool according to claim 3, wherein a cross-sectional area of the outer port hole (45a) is enlarged by increasing a port hole diameter (R ₂ ). 5. The cross-sectional area of the outer port hole (45a) is enlarged by increasing a leg opening angle (α) of legs (44b) and (44c) forming the port hole (45a). Item 3 or 4
4. The tool for porous extrusion according to item 1.